All Questions
Tagged with lie-groups smooth-manifolds
58 questions
2
votes
1
answer
122
views
Slowly increasing smooth mappings with values in a Lie group?
Let $G$ be $l$-dimensional compact Lie group and consider any smooth $F : \mathbb{R}^n \to G$.
Then, the first-order derivative of $F$ at each $x \in \mathbb{R}^n$ can be regarded as a linear mapping $...
- 286
0
votes
0
answers
87
views
Some details about Kirillov-Kostant Poisson bracket
Let $G$ be a finite dimensional Lie group with Lie algebra $\mathfrak{g}$. The Kirillov-Kostant Poisson bracket on $\mathfrak{g}^*$ is defined as $$\{\cdot ,\cdot \} :C^{\infty}(\mathfrak{g}^*)\times ...
- 287
12
votes
1
answer
379
views
Approximate classifying space by boundaryless manifolds?
As pointed out by Achim Krause, any finite CW complex is homotopy equivalent to a manifold with boundary (by embedding into $\mathbb R^n$
and thickening), and so every finite type CW complex can be ...
- 12.9k
11
votes
2
answers
838
views
Neighborhoods of the identity in diffeomorphism groups
Finite dimensional Lie groups have the nice property that if $V$ is a small neighborhood of the identity, and $U \subset V$ another neighborhood, then $V$ is covered by $U^k$ (the set of all products ...
- 35.5k
3
votes
0
answers
94
views
The tangent bundle of $G \times_H M$
Let $G$ be a Lie group with a closed subgroup $H$, and let $M$ be a smooth $H$-manifold. I am searching for a reference where it is proved that the tangent bundle of $G \times_H M$ is isomorphic to ...
1
vote
0
answers
205
views
Fourier transform of functions mapping manifolds, is there a definition?
$\DeclareMathOperator\SO{SO}$I have a problem which boils down to the analysis of functions of the form
$$
f : \mathbb{R} \to \SO(3)^n
$$
Since $\SO(3)$ is a compact group so is $\SO(3)^n$.
Now if ...
- 63.9k
7
votes
1
answer
394
views
On fixed point sets of actions of compact Lie groups
Let a compact Lie group $G$ act smoothly on a compact smooth manifold $M$. For any compact subgroup $H\subset G$ denote by $E^H$ the image in $M/G$ of the fixed point set of $H$ in $M$.
Is it true ...
- 63.9k
3
votes
1
answer
337
views
Path lifting property for $\pi:M\rightarrow M/G$ for $G$ compact Lie acting smoothly and freely
Let $M$ be a smooth manifold and let $G$ be a compact Lie group acting smoothly and freely over $M$. Let $\pi:M\rightarrow M/G$ be the canonical projection, and endow $M/G$ with the unique ...
- 8,529
3
votes
1
answer
273
views
Classification of "homogeneous" submanifolds of ℝⁿ
I define a subset $M$ of $\mathbb R^n$ to be a "homogeneous Euclidean manifold" if:
it is a closed connected smooth submanifold of $\mathbb R^n$,
for every $p, q$ in $M$, there is a ...
CommunityBot
- 1
8
votes
1
answer
599
views
Exact condition for smooth homogeneous to imply Riemannian homogeneous for compact manifolds
Let $ (M,g) $ be a homogeneous Riemannian manifold. That is, the isometry group $ Iso(M,g) $ acts transitively on $ M $. Let $ \pi_1(M) $ be the fundamental group of $ M $. Then $ \pi_1(M) $ has ...
- 4,081
4
votes
0
answers
132
views
Coordinates on quotient manifold $\mathrm{SO}(3)/\Gamma$
$\DeclareMathOperator\SO{SO}$Say I have coordinates for $\SO(3,\mathbb{R})$, e.g., a parametrization by Euler angles. Is there a reasonable way to explicitly prescribe coordinates on the quotient ...
- 63.9k
1
vote
1
answer
345
views
Is the manifold of complex points of a quotient of compact groups just the tangent bundle?
In great generality a Lie group mod its maximal compact subgroup is contractible (for example this is true for all connected Lie groups). Whenever this is true then the Lie group $ D $ is ...
- 4,081
4
votes
1
answer
369
views
A Fréchet space characterization of smooth structures on topological spaces?
For a compact manifold $M$ the space of smooth functions $C^{\infty}(M)$ is a Fréchet space where the seminorms are the suprema of the norms of all partial derivatives. Is there some way to ...
- 391
5
votes
0
answers
135
views
Specify the embedding of Lie groups (via the representation map) precisely as the embedding of two differentiable manifolds
How do we specify the embedding of a Lie group $G_1$ as a subgroup into a larger Lie group $G_2$, with $G_1 \subset G_2$ that agree with a constraint on the mapping between their representations?
By ...
- 10.5k
3
votes
1
answer
152
views
Model geometry uniqueness
Let $ M $ be a compact connected manifold with
$$
M \cong \Gamma \backslash G /H
$$
where $G $ is a Lie group, $ H $ a compact subgroup, $\Gamma $ a discrete subgroup, and $ G/H $ is connected and ...
CommunityBot
- 1
8
votes
1
answer
298
views
How special are homogeneous spaces?
Let $M$ be a smooth finite dimensional manifold, how restrictive is it to require $M$ to admit a smooth action by a finite dimensional Lie group $G$?
Related questions/approaches: Of course we need $\...
- 8,098
1
vote
1
answer
186
views
A question regarding the action of a Lie subgroup
Suppose $H$ is a closed subgroup of a Lie group $G$. Then in Lee's book Introduction to Smooth Manifolds (Ch. 9) he showed that the action $H\times G\to G$ $(h,g)\mapsto gh$ is a smooth, free, proper ...
- 12.9k
2
votes
1
answer
250
views
Embedding of the adjoint group into $\mathrm{GL}(\mathfrak{g})$
Given a connected Lie group $G$ with corresponding Lie algebra $\mathfrak{g}$, the adjoint representation/action $\mathrm{Ad} : G \to \mathrm{GL}(\mathfrak{g})$ induces a Lie group homomorphism. It's ...
- 3,065
3
votes
1
answer
370
views
Genericity of equivariant embeddings
I'd like to ask an equivariant version of this question.
Let $M$ be a closed manifold equipped with the action of a compact Lie group $G$. By the Mostow-Palais embedding theorem, $M$ can be embedded ...
- 1,040
5
votes
0
answers
157
views
Typical preimage of the commutator map
By Goto's theorem for any compact connected semisimple Lie group $G$ of dimension $n$, any element $x\in G$ is a commutator, namely $x=[y,z]$ for some $y, z\in G$. Another way to say it is that the ...
- 728
3
votes
0
answers
153
views
Diffeomorphisms fixing origin and boundary
Let $D^n$ be a disc in $\mathbb{R}^n$. Is there a known characterization of all the diffeomorphisms of $D^n$ fixing the origin and boundary of $D^n$?
- 7,583
3
votes
0
answers
58
views
Criteria for density of subgroup of diffeomorphism group
Let $C^{\infty,\star}(\mathbb{R}^d)$ denote the non-commutative topological group of smooth diffeomorphisms from $\mathbb{R}^d$ to itself with $\circ$ as multiplication and let $\emptyset\subset X\...
- 63.9k
2
votes
3
answers
294
views
Space of representations of surface group into Lie groups
In the context of Goldman's paper The symplectic nature of fundamental groups of surfaces:
Consider a closed oriented surface $S$ with fundamental group $\pi$, and let $G$ be a connected Lie group. ...
- 63.9k
4
votes
2
answers
2k
views
Fixed points of the action of an algebraic group
Hello!
If a compact Lie group $K$ acts smoothly on a smooth manifold $M$, then the set $M^K$ of fixed points under this action is a smooth submanifold of $M$. This is proved for example in ...
- 12.9k
3
votes
2
answers
2k
views
Is a manifold paracompact? Should it be?
We will say that a Hausdorff topological space $X$ is a smooth manifold if there is an open cover $(U_{\alpha})$ of $X$ and a corresponding collection of homeomorphisms $\varphi_{\alpha} : U_{\alpha} \...
- 37.8k
3
votes
0
answers
864
views
Non-Abelian fundamental group? --- a bizarre example
For the quotient space $G=G_0/G_1$, knowing the homotopy
groups of $G_0$ and $G_1$, one can determine homotopy groups from the long
exact sequence
$$
...
\to \pi_n(G_1) \to \pi_n(G_0) \to \...
- 63.9k
2
votes
1
answer
501
views
Is $H$ closed in $G$?
Every smooth manifold is assumed to be Hausdorff and second-countable.
Suppose $G$ is a Lie group, $H$ is a Lie subgroup of $G$, $N$ is a closed Lie subgroup of $G$ such that $N$ is normal, $N\cap H=\...
- 63.9k
5
votes
1
answer
153
views
Is $S$ a smooth submanifold of $M$?
Let $G$ be a Lie group and $H$ a Lie subgroup of $G$.
Let $M$ be a smooth manifold.
Let $\theta$ be a left smooth action of $G$ on $M$.
Let $S=\{p\in M| G_p=H\}$, where $G_p$ is the isotropy ...
- 26.3k
5
votes
1
answer
339
views
Boundary of the image of a compact manifold in the complex plane
The Question
Consider the trace of an $n \times n$ unitary matrix with determinant 1
\begin{align}
f: SU(n) &\rightarrow \mathbb{C}\\
U \mapsto \text{tr}\, U &= \sum\limits_{i=1}^{n-1} z_i + \...
CommunityBot
- 1
5
votes
2
answers
377
views
Existence of an isotopy in Riemannian manifold
Let $(M,g)$ be a Riemannian manifold, and $p,q\in M$ be two fixed points. We assume $p,q$ are close enough. Say, we assume $p$ and $q$ are in the same normal coordinate chart. It is clear that there ...
- 28k
13
votes
4
answers
2k
views
The Schwartz Space on a Manifold
I asked this question a couple of days ago on math.stackexchange, but have yet to receive a response, so I have decided to post this here.
This question is also vaguely related (both questions arose ...
- 5,407
2
votes
0
answers
156
views
Condition on a Lie groupoid to be represented by manifold/group or an action groupoid
Let $\mathcal{G}$ be a Lie groupoid. I am thinking of following questions.
When do we know $\mathcal{G}$ is weakly/Morita equivalent to a Lie groupoid of the form $(G\rightrightarrows *)$ for some ...
- 6,023
5
votes
1
answer
355
views
Nonlinear sigma models with non-compact groups / target spaces
A nonlinear σ model (NLSM) describes a scalar field Σ which takes on values in a nonlinear manifold called the target manifold T.
The target manifold T is equipped with a Riemannian metric g. Σ is ...
- 33.3k
6
votes
0
answers
634
views
Quotient space, a fundamental group, and higher homotopy groups 2
Previously, I ask for comments/suggestions on setting up the calculation in Quotient space, homogeneous space, and higher homotopy groups. There, however, I was looking for whatever methods and tools ...
- 10.5k
7
votes
0
answers
1k
views
Quotient by a non-free action of a Lie group and manifolds with corners
The quotient manifold theorem says that
If $G$ is a Lie group acting freely and properly on a smooth manifold $M$ then $M/G$ has a (unique) smooth structure such that the projection $\pi:M\to M/G$...
- 2,533
9
votes
1
answer
725
views
Sullivan conjecture for compact Lie groups
Let $G$ be a topological group, and $M$ a connected compact smooth manifold. I'm studying
$$ \pi_0 (map (BG,M)). $$
For $G$ a finite group, we know that this is just a point by the Sullivan ...
- 11.1k
9
votes
1
answer
807
views
Formal vector fields vs. (standard) vector fields
Given a smooth manifold $M$, one can consider the Lie algebra $\mathcal{X}(M)$ of vector fields equipped with the standard Lie bracket. This is a standard machinery of differential geometry. Gelfand ...
- 1,238
4
votes
1
answer
236
views
Submanifold of a Lie group whose tangent bundle is invariant under group (left) action
Edit: According to the interesting comment of Tobias Fritz we revise the question.
Assume that $G$ is a Lie group and $M\subseteq G$ is a closed connected smooth submanifold of $G$ containing the ...
- 1,540
3
votes
1
answer
900
views
A cut-off function with controlled gradient
Suppose a Lie group $G$ acts properly on a manifold $M$. Let $\pi: M\rightarrow M/G$ be the projection.
One can construct a bounded, smooth "cut-off" function $$c:M\rightarrow [0,\infty),$$ with two ...
CommunityBot
- 1
3
votes
0
answers
94
views
Cohomology of boundary of locally symmetric space
Let $S$ be a locally symmetric space, not necessarily compact, and $\overline{S}$ be its Borel-Serre compactification. Let $\partial S$ be the boundary of $S$. Let $\widetilde{\mathbb{C}}$ be the ...
- 63.9k
17
votes
3
answers
5k
views
one-parameter subgroup and geodesics on Lie group
Hi,
Given a Matrix Lie Group, I would like to know if the one-parameter subgroups (which can be written as $\exp^{tX}$) are the same as the geodesics (locally distance minimizing curves). Geodesics ...
- 285
5
votes
0
answers
477
views
What is the dimension of $M/G$ if it is a manifold and $G$ acts freely and smoothly?
Let $G$ be a Lie group acting smoothly and freely on a smooth manifold $M$. Suppose that the quotient space $M/G$ is a topological manifold. Do we have
$$\dim(M/G)=\dim M-\dim G?$$
Notes: This ...
CommunityBot
- 1
5
votes
1
answer
720
views
Poincaré–Bendixson theorem on the torus
I was reading the paper A Generalization of a Poincaré-Bendixson Theorem to Closed Two-Dimensional Manifolds by Arthur J. Schwartz which proves the following theorem:
THEOREM. Let $M$ be a ...
- 18.7k
5
votes
1
answer
316
views
Differential structures on compact Lie groups
Given a compact Lie group can there be a differential structure on it with respect to which one cannot define a smooth group operation?
CommunityBot
- 1
3
votes
1
answer
98
views
Locally nilpotent algebraic section of tangent bundle is complete?
Suppose $X$ is a smooth affine algebraic variety over $\mathbb{C}$ and let $V$ be an algebraic vector field (i.e. an algebraic section of the tangent bundle). If $V$ is locally nilpotent, meaning that ...
- 26.3k
0
votes
1
answer
134
views
full set of invariant functions on manifold
Let $M$ be a smooth manifold and $G$ a Lie group acting properly on $M$. Let $k$ be the codimension of a maximal dimensional $G$-orbit in $M$.
Is it always possible to construct $k$ functions $f_1, \...
- 3,652
12
votes
3
answers
849
views
$A_{\infty}$-structure on closed manifold
Is there an exmaple of a closed smooth connected manifold $M$ having a structure of $A_{\infty}$-space (with unit) but $M$ is not homeomorphic to a compact connectd Lie group as space ?
Edit: First, ...
- 1,974
2
votes
1
answer
120
views
$E \times_H \mathbb{R}^n$ is isomorphic to the total space of the tautological bundle $\gamma^n$ over $G_n(\mathbb{R}^{n+k})$?
Let $H$ be the subgroup of $\text{GL}(n + k, \mathbb{R})$ consisting of matrices whose lower $n \times k$ block is empty; i.e. consisting of matrices of the form$$\begin{pmatrix} A & * \\ 0 & ...
- 666
0
votes
1
answer
1k
views
cartan killing metric [closed]
I know that we can define the killing form on a lie algebra. However, when going to the group manifold, does this give rise to a metric on the manifold? I thought that would be the case, but I cant ...
- 4,920
1
vote
1
answer
499
views
Existence of a fixed-point free map in a manifold [closed]
I'm having some to proof a question. I have to show that a compact manifold that admits a nowhere vanishing smooth vector field has a smooth map fixed-point free homotopic to the identity map.
I know ...
- 96.4k